The present invention relates to improvements to enhance the performance, durability and manufacturability of the Migrating Combustion Chamber (MCC) engine. Reference is made to two types of MCC engines which these improvement features will apply to. The first applicable type of the MCC engine is the full expansion variant described in U.S. Pat. Nos. 4,325,331 and 4,437,437. A second type of MCC engine which can benefit from these same improvements is the self-supercharged two stroke MCC engine as described in U.S. Pat. Nos. 3,630,178 and 5,341,774. Even though these two types of engines operate with totally different cycles of operation, their basic MCC mechanism is fundamentally the same and the improvements set forth in this patent will generally apply to each type. In some instances where in the disclosed feature is applicable to one specific type, the type will be referenced.
The present invention thus describes a number of important features which have been developed from an aggressive in-house development program directed toward advancing the MCC engine into the commercial market place. These features now enable the MCC engine to be highly competitive with the present commercially available engines in three major improvement areas. These areas are:
Performance--Dealing in power, economy, lower pumping losses, lower emissions, thermal dissipation and features to enhance fast burn.
Durability--Dealing in longer life, lower thermal stress, reduced sliding forces and lubrication features.
Ease of Manufacture--Construction expedients, simplification features and combining functions to simplify manufacturing.
Accordingly, the first areas of improvement to be described are the following features to enhance performance:
Strip Seal Pressure Backing--Performance gains in terms of achieving more stable operation and also to produce higher torque at a high brake mean effective pressure are directly related to provisions incorporated into the seals and the associated working parts to assure the seal is always pressed against the two primary sealing surfaces as compression, ignition and expansion are completed. A method is disclosed which illustrates how the pressure developed in the combustion chamber during compression, ignition and expansion is routed in behind the seal to keep the seal properly engaged with the sealing surface. The pressure backing feature disclosed in this invention describes certain provisions to be made to both the strip seals and also to the working members such as the orbiting piston (OP) and Combustion, Chamber Member (CCM) in order to properly route the pressure around and in back of the seal. Thus, it is a first object of this invention to provide a means to improve performance over a broad range of loads and rotational speeds.
A second provision of this invention is to incorporate a means to increase fuel efficiency in the case of the full expansion variant of this engine by the incorporation of certain side ports located in the front and rear power blocks. These ports provide a better means to precisely control the closing of the secondary expansion chamber from the main combustion chamber relative to the closing of the induction port. The increase in fuel efficiency results from the ability to trap more of the combustible mixture in the combustion chamber with less chance of diverting a portion of it to the secondary expansion chamber. Therefore a second objective of this invention is to provide a more fuel efficient MCC engine.
A further aspect of this invention is to reduce the internal pumping losses during the exhaust gas extraction stroke of the full expansion variant of this engine. A method to change the timing by incorporating a rotary valve to control the point in the cycle when the exhaust gas begins to be pumped out will be described as to how the undesirable flow of exhaust gas back into the secondary expansion chamber can be virtually eliminated. Yet a further object of this invention will be to incorporate rotary valve porting control to reduce pumping losses with an attendant increase in fuel efficiency.
Another primary object to boost performance of the MCC engine is to provide the largest exhaust port area through the orbiting piston to achieve the lowest possible pumping losses during the exhaust function. Accordingly, it has been found that a very specific exhaust gas port shape in the OP will allow efficient exhaust gas extraction without exposing the induction ports to the exhaust gas ejection process. A further object of this invention is to describe the dimensional configuration between the OP exhaust port shape and this relationship to the induction ports to achieve non interacting porting functions along with the lowest possible exhaust gas pumping losses.
Further performance enhancement features which improve the efficiency of combustion and improve fast burn are yet a further object of this invention. A first technique to improve the fast burn characteristic of combustion involves establishing a specific relationship between the location of the ignition source in the center power block relative to the position of the orbiting piston when ignition should occur. It has been found by extensive research that the ignition source should be located in a position which is directly centered within the combustion chamber cavity of the combustion chamber member at the instant ignition is instigated. A specific relationship between the phase angle of the orbiting piston and the ignition source location in the center power block is identified relative to the exact timing angle required for optimum combustion efficiency.
A second fast burn enhancement feature is the utilization of a separate alloy steel connecting bar in which two are required to connect the ends of the two CCM segments together. This bar is designed to operate at a high temperature to promote rapid evaporization and "on time" ignition to further enhance the fast burn characteristics of the MCC engine. A specific method of attachment to the CCM segments and the physical characteristics of this bar required to enhance combustion efficiency are disclosed.
It is thus a further intent to add these special features to allow even faster more reliable combustion and burning of various grades of fuels including low octane fuels in order to keep time losses very low in the quest to achieve higher thermal efficiency.
Accordingly, it is a further intent of this invention to provide certain improvements to the MCC engine in order to enhance its durability and improve areas of its design to providce a longer life, lower thermal stress and lower sliding forces between the sliding surfaces.
Particular importance in analyzing areas of concern dealing with durability, seems to focus on thermal related problems. Hence the first durability improvement disclosed in this invention is the incorporation of a method to mechanically distort the manifold relative to the rear power block of this engine to reduce the effects of differential expansion. It has been found that if the rear mounted manifold is hard mounted (screwed on tight) to the rear power block, a thermal differential condition will occur between the hot rear power block and the relatively cooler manifold. The reason this happens is that under operational conditions the manifold maintains a lower temperature due to the flow of cool induction mixture through it. On the other hand, the rear power block operates at a higher temperature due to the exposure to the high temperature of combustion on the other side. Therefore, if the manifold is tightly affixed to the rear power block a difference in expansion between the two components will cause the rear power block to bow in in the center. This inward distortion will tend to push the rear power block against the internal moving parts causing a high degree of friction and wear. Therefore a method to counter act the effects of this distortion is disclosed in this invention which will allow a low friction interface and improved durability.
A second item to improvement durability is also related to a thermal expansion problem. The Combustion Chamber Member (CCM) has an area which operates at a higher temperature than the rest of this part. This area is associated with and surrounds the CCM interface with the connecting bars. Since the connecting bars are now used as evaporator bars they are operating at a very high temperature. Since this thermal energy is absorbed into the CCM interface, the CCM can be modified by machining an area off each side of the interface point to eliminate a situation of the high expansion causing undo friction and wear at this point. Thus, a simple machined relief of this area is disclosed which when incorporated will enhance lower operating friction and yield an associated longer life.
Finally, disclosure of three items as manufacturing expedients is made a part of this invention.
The first disclosure intended to reduce the cost of manufacture, is the utilization of a one piece counter-weight hub which utilizes a longitudinal slot and clamping arrangement to fasten the hub securely to the crankshaft. The object of this invention is to provide a combination of features within one single item to help economize the cost of the engine. Instead of providing separate counterweights, each attached separately to the crankshaft, this invention combines two independent counterweights which incorporates them into a single part together with a unique method of clamping the entire unit to the end of the crankshaft. U.S. Pat. No. 5,341,774, FIG. 2 shows a one piece counterweight hub with the location of the integral counterweights 20 and 21. However, this invention discloses how this single unit can be improved to contain a slot and clamping arrangement to align and securely fasten this part to the crankshaft in order to provide an important cost saving feature to the manufacture of the MCC engine.
A second cost saving feature to be disclosed is a one piece induction and exhaust manifold. The object of this invention is to combine the induction tract necessary to supply the carbureted mixture into the induction ports of the engine together with an exhaust tract which is necessary to channel the exhaust gases from the exhaust port out to an exhaust hose or conduit, all into one integrated part. Other desirable features of this one piece integrated unit will be disclosed which also point out certain thermal and sealing advantages. However, as a one piece unit which combines two important functions into one part, it's one significant advantage is its cost savings' impact on the MCC engine.
A final manufacturing expedient is disclosed which utilizes independent wear strips placed inside the center power block to provide the necessary sliding support and sealing surface for the CCM. The object of this invention is to manufacture the center power block as a one piece unit where in the high manufacturing cost of providing an ultra flat - hardened surface inside the power block for the CCM to slide on is replaced by much cheaper wear strips which are inserted into the center power block. These wear strips can be prepared as flat precision parts much easier and with far less cost by making them in large quantities on standard machines outside of the engine's power block.
Accordingly the intent of this invention is to describe a number of very important enhancement features. Some of these are disclosed to improve performance, others are disclosed to improve durability and cost of manufacturer; but more importantly all of these features are disclosed for the reason that these features are being incorporated into the current MCC engine design which will be manufactured and sold as a viable alternative and competitive engine.
These features and objects of the present invention will be more clearly understood from a perusal of the following detailed description read in conjunction with the accompanying drawings in which: